Method of producing hollow objects



v. GONDA 1,995,977

METHOD OF PRODUCING HOLLOW OBJECTS March 26, 1935.

Filed July 26, 1932 Patented Mar. 26, I935 I JUNITED STATES PATENT OFFICE Application July 26, 1932, Serial No. 624,860"

In Hungary February l6, 1931 1 Claim. (01. 1858)" The pressing of materials capable of being 'stance substances which contain gas-evolvingconformed into shapes in hot condition is effected by ,stituents, such as bituminous substances, resins, filling the heated material into a mould of suitartificial resins, also aqueous emulsions or soluable form, consisting, as a rule, of two parts, and tions of such substances in volatile solvents and 5 after one part of the mould has been fixed in a the like) heated atleast up to the point where the 5 suitable manner, allowing mechanical forcesto gases commence to be evolved, is filled into a act on'the other-part of the mould. The pressmould which is capable of being hermetically ing forces (pressures) employed in this manner sealed. Themould is then revolved about its longiact in their totality in one direction only, viz, tudinal axis and heated from the outside, whereinthe direction of the displacement of the movby the evolution of the gases from the material in 10 'able part of the mould; it is preferable to make the mould is assisted. After the desired internal the pressing forces actin the direction of the pressure is reached the supply of heat is dissmallest dimension of the object to be produced continued and the mould suddenly cooled down, by pressing. The mechanical force (I) referred to above is When producing hollow objects by means of produced by the hermetically closed mould con- 15 pressing, the mould employed is fitted with a core taining the material which is plastic or liquid corresponding to the cavity. In such cases it is .when in the hot state being revolved, whereby a. preferable, in order to obtain as uniform compneumatic core is formed in it. pression as possible, to employ the pressure in The physical 'force (II) is the pressure directed the direction of the axis of the core, even in the from the inside to the outside of the gases and 20 case in which this direction does not coincide with vapours evolved from the material through the the direction of the smallest,dimension of the supply of heat to the mould. The mould into object; compression will not be uniform particwhich the preheated material is introduced may ularlyin the case of the production by means be cold or it may be preheated. The further of pressing of objects, the dimension in the direcsupply of heat to the mould or to the material 25 tion of the axis of the cavity of which is many may be-efiected in any suitable manner. times their other dimension (for instance, of Owing to the fact that during the revolving tubes) because whilst the material situated in motion of the mould. a pneumatic core is formed the direction of pressure at the two extremities in the heated material, which replaced the usual of the object will be compressed in the necessary solid core, the gases and vapours evolving from 30 a degree, the compression of the material situated the material can escape to the pneumatic core. in the middle part of the object will be insufii- By this means the pressure within the moulded cient or in an extreme case the last-named maarticle is gradually increased and the material terial may possibly not receive any compression is pressed with increasing force against the inat all. y side of the mould wall. Consequently not only 35 In such cases a pressure, the direction of which is the material compressed both bythe mechanical is perpendicular to the axis of the cavity, but centrifugal force and by the continuously increaswhich acts simultaneously and in an equal maning physical pressure of thegases and. vapours ner in the direction of all lines perpendicular to imprisoned in the cavity of the article, but, owing the said axis is the most advantageous, because to the fact that the gases can escape freely out 40 it enables uniform compression to be obtained, of th material, completely non-porous and Owing to the fact that the Object will receive homogeneous, solid moulded articles are obtained. in its totality, and everywhere in the direction The physical fo e 11 is produced by th its Smallest dimension pres sure of equal sudden cooling of the metal mould which has exmtufie and equal Sense This end Qannot be panded through being heated, causing the mateachleved by the emplpyfnent of mechafmcal forces rial of the mould to contract and to exert on the alone and therefore 1t 15 endeavored in the procmaterial being moulded a compressive force ess mmmg the sublect matter the present which is oppositely directed to the forces (I) and patent to obtain the optimum pressure, i. e. a pressure acting simultaneously and in an equal (II). This produces a further compression of the measure in the direction of all the lines permoulded artlclependicular to the longitudinal axis of the cavity, In the p y g d awing a constructional by employing one h i m force 1 and t example of the apparatus according to the invenphysical forces II, III. tion for carrying outthe present process is shown.

With this object in view the material (for in- Fig. 1 is a longitudinal cross sectional view of 55 end views of the respective ends 01' Fig. 1.

Into the metal mould a which is adapted to be closed in an air or gas-tight manner and the in- 4 cover.

terior shape of which corresponds to the exterior shape of the article, the material is introduced after being heated, or after being made plastic or liquid by heat at least up to the point where gas or vapour will commence to evolve, whereupon the mould which for the purpose is open on one .sideis hermetically closed with a The mould held fastby means of the shaft i in the bearings 01 and c2 and supported at its other end by rollers di and (12 is arranged so as to be rotatable around the longitudinal axis of the cavityto be formed. The filled mould is with the aid of the pulley e made torotate at a speed of about 500 revolutions per minute and at the same time the whole mould is heated from any desired source of heat, conveniently by means of oil burners lc. After the heating period cooling water is passed through perforated tubes 1 provided for this purpose. The water passes out 01 the openings of the tubes 1 against the walls of the rotating cylindrical mold a and thereby cools thesame. By means of the centrifugal. force set up owing to the high number of revolutions perminute, the soft material is pressed to the inside surface of the metal mould which has become expanded owing to the heat imparted to it, a pneumatic core being formed inside the mould. The material is formed and at the same time compressed through the action of the centrifugal force (force I) which depends on the number of revolutions employed. Simultaneously with this force and in the same sense a compres-. sive force acts, which is produced owing to the supply of heat on the one hand by the gases escaping out of the material and on the other hand through the expansion of the air imprisoned in the pneumatic core, and the magnitude of which is dependent on the quantity or temperature of the heat supply (force 11). BothYorces (I and II) act in the direction of all possible perpendiculars to the. axis of. the cavity, this action being centrifugal. Both the forces described above are allowed to act for a certain time, being if necessary increased until the desired compression of the material is reached. Thereupon the supply of heat is cut off and the mould while still revolving at the same speed is cooled down suddenly. Owing to the sudden cooling the expanded metal material of the mouldcontacts rapidly, thereby producing a compressive force (force 111) 'which-also acts in the direction of all possible perpendiculars on the axis of the cavity but in the opposite directionto the forces (1 and II) which were described above and are still effective, that is to to say in the centripetal direction.

The compressed article made in this manner is ejected from the mould by means of a plunger in the followingmanner. The screw spindle gis connected to the shaft i by a keywand keyway positively in such a manner that it can move freely only parallel to the shaft. If thefree part of the screw spindle projecting from the shaft be held fast close to the shaft and during the rotation of the latter by means-01 a two-part fixed nut, the spindle g and the plunger ,1 connected to it will move the axial direction and push the finished pressed article which is inthe mould out of the latter. The emptied mould is rotated about the pivot h into a vertical position, in which position it can be easily and rapidly filled. The filled mould is thereupon closed again by means of the cover b and brought into the horizontal position, when the Dressing operation can be repeated. i a

What I claim is:

A method of forming hollow bodies" from ma:

terial capable of being formed whenin a warm state, more particularly from material containing' substances which when heated evolve gases, consisting in introducing the material heated at least to a temperature, at which the evolution of gases'will commence, into a mold, closing the mold in. ages-tight manner, imparting'a rotary motion to the mold and heating the mold simultaneously'thereby'causing a pneumatic core to form in the material by gases evolved out of it, cutting off the supply of heat and suddenly cooling down the mold.

VILMOS GONDA. 

